Mechanically stacked 1 nm thick carbon nanosheets: Ultrathin layered materials with tunable optical, chemical and electrical properties

Carbon nanosheets are mechanically stable free-standing two-dimensional materials with a thickness of ~1 nm and well defined physical and chemical properties. They are made by radiation induced cross-linking of aromatic self-assembled monolayers. Here we present a route to the scalable fabrication of multilayer nanosheets with tunable electrical, optical and chemical properties on insulating substrates. Stacks up to five nanosheets with sizes of ~1 cm^2 on oxidized silicon were studied. Their optical characteristics were investigated by visual inspection, optical microscopy, UV/Vis reflection spectroscopy and model calculations. Their chemical composition was studied by X-ray photoelectron spectroscopy. The multilayer samples were then annealed in ultra high vacuum at various temperatures up to 1100 K. A subsequent investigation by Raman, X-ray photoelectron and UV/Vis reflection spectroscopy as well as by electrical four-point probe measurements demonstrates that the layered nanosheets transform into nanocrystalline graphene. This structural and chemical transformation is accompanied by changes in the optical properties and electrical conductivity and opens up a new path for the fabrication of ultrathin functional conductive coatings.Comment: 36 pages, 7 Figure

With greater power comes greater responsibility? takeover protection and corporate attention to stakeholders

Using takeover protection as an indicator of corporate governance, this study examines how an exogenous shift in power from shareholders to managers affects corporate attention to non-shareholding stakeholders. Two competing hypotheses are entertained. The shareholder view predicts that stronger takeover protection will lead to a decrease in corporate attention to shareholders and non-shareholding stakeholders alike, as managers divert resources from shareholders to the pursuit of their private interests. The stakeholder view, in contrast, predicts that stronger takeover protection will increase corporate attention to non-shareholding stakeholders. Because catering to non-shareholding stakeholders contributes to the long-term value of the firm, managers will be more likely to attend to those stakeholders when relieved from short-termism triggered by the threat of hostile takeovers. Using a sample of 878 U.S. firms from 1991 to 2002, the study finds that an exogenous increase in takeover protection leads to higher corporate attention to community and the natural environment, but has no impact on corporate attention to employees, minorities, and customers. Additional analyses show that firms that increase their attention to stakeholders experience an increase in long-term shareholder value. These findings provide additional evidence that relief from short-termism is a likely source of the increase in corporate attention to non-shareholding stakeholders following the increase in takeover protection. Copyright © 2008 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61437/1/733_ftp.pd

Conversion of self-assembled monolayers into nanocrystalline graphene: Structure and electric transport

Graphene-based materials have been suggested for applications ranging from nanoelectronics to nanobiotechnology. However, the realization of graphene-based technologies will require large quantities of free-standing two-dimensional (2D) carbon materials with tuneable physical and chemical properties. Bottom-up approaches via molecular self-assembly have great potential to fulfil this demand. Here, we report on the fabrication and characterization of graphene made by electron-radiation induced cross-linking of aromatic self-assembled monolayers (SAMs) and their subsequent annealing. In this process, the SAM is converted into a nanocrystalline graphene sheet with well defined thickness and arbitrary dimensions. Electric transport data demonstrate that this transformation is accompanied by an insulator to metal transition that can be utilized to control electrical properties such as conductivity, electron mobility and ambipolar electric field effect of the fabricated graphene sheets. The suggested route opens broad prospects towards the engineering of free-standing 2D carbon materials with tuneable properties on various solid substrates and on holey substrates as suspended membranes.Comment: 30 pages, 5 figure

Firm Litigation Risk and the Insurance Value of Corporate Social Performance

Firm litigation risk and the insurance value of corporate social performanc

Herstellung von Biochips basierend auf selbstaggregierender Monolagen

Schnietz M. Herstellung von Biochips basierend auf selbstaggregierender Monolagen. Bielefeld (Germany): Bielefeld University; 2011.Die Untersuchung von Proteinen stellt besondere Herausforderungen an die Entwicklung von sogenannten Biochips dar. Hierfür sind funktionalisierte Mikro- und Nanometer Strukturoberflächen mit sehr hoher Auflösung erforderlich. Ziel ist die Immobilisierung von Biomolekülen an wohl definierten funktionellen Positionen, um eine weitere detaillierte Analyse zu ermöglichen. Die Verwendung von Selbstaggregierenden Monolagen (SAMs) ist für die oben genannten Ziele eine ideale Plattform. Durch diese Monolagen lassen sich chemische und physikalische Eigenschaften der Oberflächen sehr genau kontrollieren. Sie dienen als Bindeglied zwischen organischen und anorganischen Umgebungen. Durch verschiedene lithographische Techniken können auf diesen Oberflächen lateral definierte chemische modifizierte Strukturen erzeugt werden. In der vorliegenden Arbeit wurde die laterale Strukturierung selbstaggregierender Monolagen (SAMs) mittels EUV Interferenz Lithographie (EUV-IL) untersucht. Dabei zeigt sich, dass die direkte Strukturierung der Nitrobiphenyl-Thiol SAMs durch Vernetzung die gleichen chemischen und physikalischen Eigenschaften aufweisen wie Elektronenvernetzte Proben. Die Methode der EUV-IL eignet sich somit besonders gut für die Fabrikation von großflächigen Vorlagen wie z.B. für Biochips. Die Kombination aus SAM und EUV Lithographie basierter Technik besitzt ein enormes technisches Potential. Es lassen sich hierbei Nanosiebe oder durch Anbindung von multivalenten NTA-Derivaten an die chemisch funktionalisierte SAM mit NTA / His-tag Wechselwirkung Biochips realisieren. Diese NTA-Chelator Proteinbiochips erlauben eine spezifische, hochaffine, umkehrbare und langfristige Immobilisierung His-markierter Proteine. Deren Verwendung ist in der Untersuchung bzw. Analyse von unterschiedlichen Proteineigenschaften auf Oberflächen sehr hilfreich. Die Herstellung und Anwendung einer Vielzahl von physikalischen, chemischen und biologischen Strukturen wird hierdurch ermöglicht. Konkret konnten verschiedene Herstellungsmethoden zur Realisierung eines Biochips demonstriert werden. Außerdem können mit dem Ansatz aus SAM und EUV-IL Nanosiebe produziert werden. Dabei handelt es sich um Membrane mit einer Schichtdickenstärke und Perforation im Nanoskala Bereich. In dieser Arbeit werden definierte Porenöffnungen bis zu ~30nm gezeigt. Mögliche praktische Anwendungen sind z.B. Filter

Globalization Derailed? Multinational Investors' Response to the 1997 Denial of Fast-Track Trade Negotiating Authority

Is globalization being derailed by opponents? Results of this event study analysis of the 1997 fast-track denial suggest that investors (1) may have perceived fast-track as a debate on globalization and (2) appear to have expected financial losses to result from the failure to enact fast-track. Regression results further support the event study findings.© 2001 JIBS. Journal of International Business Studies (2001) 32, 479–496

The Reaction of Private Interests to the 1934 Reciprocal Trade Agreements Act

In recent research on the 1934 Reciprocal Trade Agreements Act (RTAA), there has been no examination of the reaction of private actors to the RTAA. Did producer groups and investors in 1934 believe the Democratic RTAA was the solution to Republican protectionism, as institutional analyses of the RTAA claim, or did they realize the RTAA was no magic bullet against a return of protectionism, as skeptics argue? Archival data suggests that many producer groups believed the RTAA would result in durable liberalization, but that fewer understood the likely effects of its specific features. An event study of investor reaction to the RTAA reveals that export-dependent firms experienced a significant, positive stock return increase on news of the RTAA, while heavily tariff-protected firms experienced a significant stock decline, albeit several months later.Many thanks to George Kanatas, David Mowery, Barbara Ostdiek, Joanne Oxley, Dennis Quinn, Duane Windsor, Bernard Yeung, two anonymous reviewers, and Peter Gourevitch and David Lake for helpful comments on earlier drafts of this paper. I am also indebted to Scott Baggett for statistical assistance and to Katie Schwenker, Helen El-Mallakh, and Clara Montz for patient research assistance.